Development of a multi-analyte CMOS sensor for point-of-care testing

A typical microarray experiment requires both a biochip on which the biological reactions take place and a microarray scanner for analysis and visualization of the data. Here, we report on the generation of a chip, which consists of a CMOS photodiode array onto which receptors are immobilized and which are used for the detection and quantification of proteins in sera solution. Such an approach allows direct electronic read-out of the chip via a computer port so that the size of the whole analytical setup is very compact, opening the avenue to the generation of simple handheld devices. ELISA reactions directly performed on the surface of the photodiode arrays are used to measure a number of serum factors with a broad range in concentrations of samples with volumes of less than 10 μl. As in physiological sera analyte concentrations of the different parameters vary frequently by several orders of magnitude, parallel competitive reactions are used to adjust the dynamic range of several ELISA tests on the chip. We show as a demonstration case that this allows to quantify simultaneously C-reactive protein, Immunoglobulin E, Cystatin C, Myoglobin and Ferritin in a single assay.